V Beam, do they work?
 

I've been modeling V beams off and on for a few years now, and never
can seem to get one that has useful gain.

Has anyone seen a successful model anyplace of a two or three wave V
with good gain??

73 Tom

V Beam, do they work?
 

wrote in message
oups.com...
I've been modeling V beams off and on for a few years now, and never
can seem to get one that has useful gain.

Has anyone seen a successful model anyplace of a two or three wave V
with good gain??

73 Tom

Hi Tom,
I have a model of a 5 wavelength 24MHz Vee beam in AO- I can send the file
if it is useful to you. AO reports 11dBi free space gain. Included angle
appears to be 44 degrees.

Dale W4OP

V Beam, do they work?
 

Dale Parfitt wrote:
wrote in message
oups.com...
I've been modeling V beams off and on for a few years now, and never
can seem to get one that has useful gain.

Has anyone seen a successful model anyplace of a two or three wave V
with good gain??

73 Tom

Hi Tom,
I have a model of a 5 wavelength 24MHz Vee beam in AO- I can send the file
if it is useful to you. AO reports 11dBi free space gain. Included angle
appears to be 44 degrees.

I don't have AO Dave, so a description will work.

That sounds like the problem I am seeing. With a 3-5 WL long V, I have
about the same gain as a three element Yagi. But I'll still try to
model your antenna with 5wl legs and 44 degree angle. Thanks.

V Beam, do they work?
 

wrote in message
oups.com...

Dale Parfitt wrote:
wrote in message
oups.com...
I've been modeling V beams off and on for a few years now, and never
can seem to get one that has useful gain.

Has anyone seen a successful model anyplace of a two or three wave V
with good gain??

73 Tom

Hi Tom,
I have a model of a 5 wavelength 24MHz Vee beam in AO- I can send the
file
if it is useful to you. AO reports 11dBi free space gain. Included angle
appears to be 44 degrees.

I don't have AO Dave, so a description will work.

That sounds like the problem I am seeing. With a 3-5 WL long V, I have
about the same gain as a three element Yagi. But I'll still try to
model your antenna with 5wl legs and 44 degree angle. Thanks.

Hi Tom et al,

This is from the AO library:
F=24.94

The vertex is at the origin: 0,0
X,Y of 1st leg is 185.44', -74.92' #12 wire
X,Y of 2nd leg is 185.44', 74.92' #12 wire

Fed at the origin and modeled in free space

AO reports
Z= 255- J706
Forward gain= 11.34dBi
F/B 2.70dB


Hope this is useful,

Dale W4OP

V Beam, do they work?
 

On 22 Mar 2006 17:40:02 -0800, wrote:

I've been modeling V beams off and on for a few years now, and never
can seem to get one that has useful gain.

Has anyone seen a successful model anyplace of a two or three wave V
with good gain??

Tom,

Some questions.

What is "good" gain?

What frequency?

How high?

Try this at 10 MHz. Dimensions in feet.

End 1 End 2

X Y Z X Y Z

W1 0.0 0.0 100.0 245.0 -114.2 100.0
W2 0.0 0.0 100.0 245.0 114.2 100.0

V Beam, do they work?
 

Thanks guys. I tried the models and they still look poor. Let me
explain a bit...

What is "good" gain?

More than a 3 element yagi.

What frequency?

Well, I was trying 160, 80 and 40. I have a 300ft support at one
point, and a bunch of 100ft trees a good distance away across open
fields (maybe 800 feet).

How high?

Anything up to 300 ft at the feedpoint.

Try this at 10 MHz. Dimensions in feet.

That antenna almost equals a three element yagi in gain, but the 3 ele
yagi has a HPBW of 60 degrees. The V beam has a HPBW of 18 degrees. Not
so good. Even if I try two V beams, one inside the other, I can only
get 3dB more gain.

I was wondering if I was missing something, because I keep hearing
stories about how good big V beams work.

V Beam, do they work?
 

V Beam, do they work?
 

I was just reading about them in the antenna handbook. The v-beam is
better than a dipole and is directional, but the same wire bent
half-way out to make a rombic seems to add more gain. you might look
into it.

Buck
N4PGW


On 22 Mar 2006 17:40:02 -0800, wrote:

I've been modeling V beams off and on for a few years now, and never
can seem to get one that has useful gain.

Has anyone seen a successful model anyplace of a two or three wave V
with good gain??

73 Tom

--
73 for now
Buck
N4PGW

V Beam, do they work?
 

V Beam, do they work?
 

On Fri, 24 Mar 2006 12:04:51 -0500, Dave wrote:

wrote:

SNIPPED

It looks like a simple antenna, has a good reputation, but it doesn't
look very useful for anything. Unless there is a combination I'm
missing.

73 Tom


I've never worked with a Vee antenna. But, while stationed at Hill AFB,
Utah we used two of them back to back to make a Rhombic :-) to support
the South East Asia phone patch nets during the Vietnam conflict. Fixed
point to point communication [We had an LP that was used for stateside
COMMs]

My understanding is that a narrow beam is formed along the axis
[centerline] of the Vee. In a standing wave antenna, the beam is
bi-directional. In a terminated antenna, traveling wave, the pattern is
unidirectional. The narrow beam width reduces interference from
undesired directions.

Tom is correct. Vee beams and rhombics have horrible sidelobes that
make them in my estimation highly overrated. The vee is not completely
bi-directional, a couple of dB FB is not uncommon. A vee, just like a
rhombic can be terminated to increase the FB. If the legs are long
enough it -is- a traveling-wave antenna and is somewhat
self-terminating.

The claim for broadband gain is also suspect. There are optimum
parameters that are not frequency independent

Of course I can't fault VK5MC's three-stack rhombic that gave me my
two-meter WAC :-)


Total wavelength and included angle have significant impact on performance.

Of course.

V Beam, do they work?
 

Dear Tom:

It appears that you are investigating a slopping, V-beam with a feed point
at about 90 meters and an operating frequency of, say, 1.82 MHz. When first
used some 80 years ago, V-beams were horizontal (or, alternatively, entirely
in a vertical plane). Two more 90 meter poles are not likely to be in the
picture.

The good news is that you are apparently interested in a narrow range of
frequencies. That is good news because aligning the lobes with their
changing polarization and orientation over a significant bandwidth is like
composing something to compete with Mozart.

Even using one frequency, it is a bear to get a slopping V to do one's
bidding. I would limit lengths to integer multiples of 0.5L that could fit
your farm. I would optimize a single, end fed wire (over ground) and in the
process find a narrow range of lengths that look promising and that fit your
site. Then add, and drive, the second wire. Iteration is called for. I
would use a figure of merit that is the gain at a TOA of something like 30
degrees.

Kraus, even in the first edition, presents several approximate equations
to optimize a horizontal rhombic. They may give a little guidance. I think
I read a Technical Report in the mid 60s on measurements of a sloping V put
out by either NBS or ESSA. I seem not able to put my finger on it just now.

As mentioned, the difficulty with sloping wires is finding a "good"
bore-site addition of fields from the two wires when those fields are, to a
first approximation, in the shape of cones with changing polarization. It
is more easy with horizontal wires.

If I live long enough to retire from teaching, this is a type of project
that would be interesting to investigate. But I only have 42 years in and
my good wife is certain that I could not stand the pace of retirement. Do
let us know what you come up with. Good luck.

73, Mac N8TT

Two side notes: My friend, HS and University classmate, and great DXer
W8TWA has used a set of sloping V-beams on HF to good effect. -- As you know
better than almost anyone, one needs a height in the neighborhood of 2L to
get serious signals from a horizontally polarized antenna at the lower TOAs
used for DX. You may find that your best sloping V-beam has a strong
vertically polarized component in the main beam.